Yes, as @gt22 rightly says, there has already been a similar subject covered.
You have to add in the general options of the other 2 stations the folder where the sldmat file to share is located. It will then appear in your list of materials.
In order for the material library to be visible to everyone, it must be put on a network folder so that everyone can access it, with the latest updates.
As jmsavoyat specified, you have to point in the right location.
Personally I don't like to point to a network file, too much latency and anyone can modify the file with its share of errors.
I made an executable in order to copy our solidworks parameter files (material, design library.....) locally applicable to the start of the workstation.
There is a simple solution, share on the network the folder containing all the SW reference documents (Model, material...), then you just have to manage the sharing of the said folder according to the users.
They must be granted the right to read for all, and to write for those who have the right to modify and add elements.
With us, BE and BMI have full access, interns and apprentices have access only to reading.
It works very well.
On the other hand for the latency... Wired network in 1GB/sec and avoid WiFi.
Put the files on a network folder. Hover over it by setting the solidwors options.
Of course, you must have access to the sharing folder and write rights to the folder.
What I added in my second post is the fact of repatriating the files locally via a script that would copy from the network folder to the local folder the solidworks parameter files.
This avoids false manipulations by the various users if unwanted modifications or others and makes the operation of solidworks more fluid.
@jordan.mouret.pro, we also have another mode of operation which is in // of the one exposed in my previous post.
In short:
1 - You put all your data common to SW (as mentioned above) in a folder on the server.
2-You set the sharing options correctly
3-On Fixed Workstations: SW folder option that points to the network folder
4-On mobile workstations (laptops), in Windows File Explorer, you connect a network drive that points to the server folder with the "available offline" option and finally you point to the SW options on the freshly connected drive.
This has two big advantages for outdoor work, you can print an SW license (or you have it on your computer) and you can work with all the useful data. When you return to the site, Windows takes care of updating the content of the drive.
It's almost magical, I have several employees who work like this and they are satisfied with it.